1. Field of the Invention
The present invention relates to a magnetic recording medium capable of recording at high density and a method of manufacturing the magnetic recording medium.
2. Description of the Related Art
In the information-oriented society in recent years, the amount of data that needs to be stored in a recording medium has been continually increasing. To keep up with the increase in amount of data, there has been a demand for a recording medium and a recording apparatus with a dramatically high recording density. As regards a hard disk for which there is an increasing demand as a high-capacity and inexpensive magnetic recording medium, it is predicted that a recording density of one terabits per square inch or more, which is about ten times higher than the current recording density, will be required several years after.
In an existing magnetic recording medium used in a hard disk, one bit is recorded in a specific region of a thin film made of polycrystals of fine magnetic grains. To raise the recording capacity of the magnetic recording medium, therefore, the recording density must be increased. For this purpose, it is effective to reduce a recording mark size usable in recording per bit. If, however, the recording mark size is simply reduced, effect of recording noise caused by the shape of fine magnetic grains cannot be neglected. Instead, if the fine magnetic grains are further reduced in size, it is impossible to maintain the data recorded in fine magnetic grains at an ordinary temperature due to a problem of thermal fluctuation.
To avoid these problems, it is proposed to use a patterned medium in which dots of recording material are separated by a non-recording material in advance so as to perform read and write using a single recording dot as a single recording cell (see U.S. Pat. No. 5,956,216).
Also, in the magnetic recording medium incorporated into a hard disk drive (HDD), there is an increasing problem of disturbance of enhancement of track density due to interference between adjacent tracks. In particular, a serious technical subject is reduction of write blurring due to fringe effect of magnetic fields from a write head. A discrete track recording-type patterned medium (DTR medium) in which recording tracks are physically separated is capable of reducing a side erase phenomenon of erasing data of an adjacent track in writing or a side read phenomenon of reading out data of an adjacent track in reading, and is capable of enhancing the track density. Therefore, the DTR medium is expected as a magnetic recording medium capable of providing a high recording density (see JP-A-7-85406). It should be noted that, because the DTR medium is a form of the patterned medium, the term “patterned medium” herein includes a bit patterned medium and a DTR medium.
In the DTR medium or bit patterned medium of a type in which recording tracks or recording cells are physically separated, it is important to fill recesses between magnetic patterns with a nonmagnetic material to flatten the surface of the medium in terms of flying stability of a head. Particularly, processes of filling with a metal and flattening of the metal reduce dust generation during sputtering and give sufficient strength against impact. However, when a pure metal such as Cr is used as the filling material, particles of tens of nanometers to hundreds of nanometers in size are formed on the surface of the medium, bringing about increase in surface roughness (Ra).
Also, the metal film is etched on the edge surface of the substrate during processed of filling and flattening, giving rise to a problem that electric conduction is not achieved on the edge surface of the substrate. For this reason, diamond-like carbon (DLC) which will be deposited by chemical vapor deposition (CVD) as a protective film for the medium can not be used. It is considered to use carbon nitride instead of DLC, but carbon nitride has a poor adhesion to the filling material made of a common metal.